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Статті в журналах з теми "Film effectiveness"
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Gartshore, I., M. Salcudean, and P. Matys. "FILM COOLING EFFECTIVENESS." Transactions of the Canadian Society for Mechanical Engineering 15, no. 1 (March 1991): 43–56. http://dx.doi.org/10.1139/tcsme-1991-0002.
Повний текст джерела
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Rahman, Nor Dawirah, Anna Lynn Abu Bakar, Wan Hurani Osman, and Mohammad Aqmal Hafidz Musa. "THE EFFECTIVENESS OF FILM REVIEW IN ENHANCING STUDENTS’ ENGLISH SPEAKING SKILLS." International Journal of Education, Psychology and Counseling 6, no. 41 (July 31, 2021): 23–37. http://dx.doi.org/10.35631//ijepc.641003.
Повний текст джерелаАнотація:
This study highlighted the effectiveness of film review in enhancing English speaking skills among students at the tertiary level. The population involved was 30 students from an Essential Communication Skills class at Universiti Malaysia Sabah. There were two parts of film review carried out for this study, namely, Part 1: Individual Film Review Presentation and Part 2: Group Discussion and 2 weeks prior, the teacher-researcher provided materials such as examples of vocabularies, grammars, phrases and sentences students could use to describe film genres, characters, themes, recommendations and criticisms in their film review. For Part 1 of the film review, in groups of 5, individual students orally presented the review of their chosen film whilst showing their power point slides whereas for Part 2, they gave ideas and opinions on the best film of those presented by their group members. The objective of this study was to identify students’ perceptions on the effectiveness of film review in enhancing their English-speaking skills. To accomplish that objective, this study employed a survey research design and the instrument utilised in the data collection was an online questionnaire comprising 10 questions on students’ perceptions on English film watching and review which was administered to 30 respondents. The data was then analysed using a google form spreadsheet and presented in pie charts and bar graphs. The findings depicted that students perceived that film review enhanced their English-speaking skills in the aspects of motivation and confidence in speaking simple English and applying appropriate English grammars, vocabularies, pronunciation, intonation, and conversational phrases in expressing ideas and opinions. They also opined that English subtitles in films and guidance from educators in reviewing films contributed positively to the development of their English-speaking acquisition as well as deduced that film review was an effective English learning tool. These positive findings hence signalled that the teaching and learning of English through films should be sustained in the future. It is recommended that future studies include larger numbers of respondents and interviews of students and teachers to obtain more holistic findings on the film review effectiveness towards students’ English-speaking competency. Other interesting topics to be studied are the challenges encountered by both learners and educators in the teaching and learning of English through films and ways to overcome them.
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Kim, Do Hyoung, Han Ki Yoon, Do Hoon Shin, and Riichi Murakami. "Electromagnetic Wave Shielding Properties of ITO/PET Thin Film by Film Thickness." Key Engineering Materials 345-346 (August 2007): 1585–88. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.1585.
Повний текст джерелаАнотація:
The thin films of indium tin oxide (ITO) are used for a variety of electronic devices such as solar cells, touch panels, liquid crystal displays (LCDs). However, these electronic devices are not strong enough against heavy impact since their ITO thin films are deposited on glass substrates. Therefore, ITO thin films were prepared by the inclination opposite target type DC magnetron sputtering equipment onto the Polyethylene Terephthalate (PET) substrate at room temperature using oxidized ITO with In2O3 and SnO2 in a weight ratio of 9:1. In this study, the transmittance, resistivity and electromagnetic wave shielding effectiveness of the ITO thin films prepared at various sputtering time (20~80min namely film thickness; 130~500nm) are measured. The results show that transmittance of the ITO thin films could show about 70% in the range of a visible ray by the variation of film thickness. It also can be seen that a minimum exists in the resistivity of ITO thin films for the variation of film thickness. Electromagnetic wave shielding effectiveness was increased as film thickness increased.
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Mathison, R. M., M. G. Dunn, M. M. Weaver, and A. Dushko. "Measurement of Air Film Damping Effectiveness." Journal of Turbomachinery 127, no. 3 (March 1, 2004): 557–63. http://dx.doi.org/10.1115/1.1928288.
Повний текст джерелаАнотація:
Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the two-stripe mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the resonant frequencies lower.
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Courtis, Matthew, Alexander Murray, Ben Coulton, Peter Ireland, and Ignacio Mayo. "Influence of Spanwise and Streamwise Film Hole Spacing on Adiabatic Film Effectiveness for Effusion-Cooled Gas Turbine Blades." International Journal of Turbomachinery, Propulsion and Power 6, no. 3 (August 31, 2021): 37. http://dx.doi.org/10.3390/ijtpp6030037.
Повний текст джерелаАнотація:
To meet the challenges of increased thermal loads and performance demands on aero-engine turbine blades, more advanced cooling techniques are required. This study used a modification of the well-known Goldstein equation to predict film effectiveness for an individual film cooling hole and applied the Sellers’ superposition method to apply these films across effusion-cooled configurations. In doing so, it tackles a relatively unchallenged problem of film holes in close spanwise proximity. An experimental set-up utilised infrared cameras to assess the film effectiveness of nine geometries of varying spanwise and streamwise spacings. Higher porosity led to increased thermal protection, and the spanwise spacing had the most profound impact, with film effectiveness approaching 0.9. Additionally, greater uniformity in the spanwise direction was observed. The modified Goldstein-Sellers method showed good agreement with experimental results although lateral mixing was underestimated. This method represents a tool that could be easily implemented in the industry for rapid assessment of novel cooling geometries.
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Mizoguchi, Makoto, Naoko Iwata, Kentaro Hayashi, Shigeru Aso, and Yasuhiro Tani. "Film Cooling Effectiveness in High Enthalpy Flows." JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 55, no. 641 (2007): 259–65. http://dx.doi.org/10.2322/jjsass.55.259.
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Sturgess, G. J. "Design of Combustor Cooling Slots for High Film Effectiveness: Part I—Film General Development." Journal of Engineering for Gas Turbines and Power 108, no. 2 (April 1, 1986): 354–60. http://dx.doi.org/10.1115/1.3239911.
Повний текст джерелаАнотація:
The metal liners of gas turbine engine combustors usually have to be provided with some form of thermal protection from the high temperatures of the reacting mixture of gases contained therein. For aircraft gas turbines, where weight is a factor, the protective medium is air. The air is most usually introduced by tangential injection as a discrete film at a number of axial stations along the combustor liner so that as the cooling potential of one film is depleted it is periodically renewed by another. Although invariably referred to as film cooling, the most important function of the film air is to act as a relatively cool barrier between the vulnerable liner and the reacting gases. The design margin for error is very small. Failure to design a cooling slot that provides a high film effectiveness can result in thermal damage to the liner. Manufacturing considerations almost always determine how a real slot design is reduced to practice. The resulting liners (inner and outer in the case of an annular combustor) contain no two slots that are exactly alike in aerodynamic behavior and, therefore, in film effectiveness performance. Phenomenological models of the film cooling process are invariably based on considerations of two-dimensional shear mixing. Empirical factors may be introduced to account for the differences in performance existing between two-dimensional film slots and real slots. However, such methods are not of much help in designing a slot configuration that will deliver good performance, for making comparative evaluations of competing designs, or in establishing the performance penalties associated with compromises made for manufacturing reasons. Heuristic arguments are used to derive a dimensionless grouping of internal geometric parameters that describe the lateral aerodynamic uniformity of the films produced by practical slots. It is assumed that the average film effectiveness is uniquely related to the film lateral uniformity. Experimental data from a number of different practical slot designs are examined in terms of this geometric mixing parameter, and film effectiveness is shown to depend on it over a wide range of axial distances and film blowing ratios. It is concluded that the geometric mixing parameter provides a means to differentiate good film cooling slot designs from poor ones.
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Jumper, G. W., W. C. Elrod, and R. B. Rivir. "Film Cooling Effectiveness in High-Turbulence Flow." Journal of Turbomachinery 113, no. 3 (July 1, 1991): 479–83. http://dx.doi.org/10.1115/1.2927899.
Повний текст джерелаАнотація:
The mechanisms influencing film cooling effectiveness on a flat plate in high free-stream turbulence using a single row of 30 deg slant-hole injectors are examined. The primary area of focus is the area within 40 diameters downstream of injection. Of interest are blowing ratios for optimum film cooling effectiveness within 10 diameters downstream of injection, and the decay of film cooling effectiveness down the plate. Film cooling flow Reynolds numbers. Re, from 24,700 to 86,600 and free-stream turbulence intensities from 14 to 17 percent were examined. Changes in Reynolds number or free-stream turbulence broadened and increased the blowing ratios for optimum film cooling effectiveness. In comparison with tests conducted at 0.5 percent free-stream turbulence, higher free-stream turbulence causes a faster decay in film cooling effectiveness, or a reduction in the effective cooling length, and a reduction of the level of cooling effectiveness at the higher Reynolds numbers.
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Cheng, Hung-Chuan, Chong-Rong Chen, Shan-hui Hsu, and Kuo-Bing Cheng. "Electromagnetic Shielding Effectiveness and Conductivity of PTFE/Ag/MWCNT Conductive Fabrics Using the Screen Printing Method." Sustainability 12, no. 15 (July 22, 2020): 5899. http://dx.doi.org/10.3390/su12155899.
Повний текст джерелаАнотація:
The management of the electromagnetic interference (EMI) of thin, light, and inexpensive materials is important for consumer electronics and human health. This paper describes the development of conductive films that contain a silver (Ag) flake powder and multiwall carbon nanotube (MWCNT) hybrid grid on a polytetrafluoroethylene (PTFE) film for applications that require electromagnetic shielding (EMS) and a conductive film. The Ag and MWCNT hybrid grid was constructed with a wire diameter and spacing of 0.5 mm. The results indicated that the proposed conductive films with 0.4 wt% MWCNTs had higher electromagnetic shielding effectiveness (EMSE) and electrical conductivity than those with other MWCNT loading amounts. The results also showed that the film with 0.4 wt% MWCNT loading had a high 62.4 dB EMSE in the 1800 MHz frequency and 1.81 × 104 S/cm electrical conductivity. This combination improved stretchability, with 10% elongation at a 29% resistivity change rate. Conductive films with Ag/MWCNT electronic printing or lamination technologies could be used for EMI shielding and electrically conductive applications.
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Okita, Yoji, and Masakazu Nishiura. "Film Effectiveness Performance of an Arrowhead-Shaped Film-Cooling Hole Geometry." Journal of Turbomachinery 129, no. 2 (June 21, 2006): 331–39. http://dx.doi.org/10.1115/1.2437781.
Повний текст джерелаАнотація:
This paper presents the first experimental and numerical work of film effectiveness performance for a novel film-cooling method with an arrowhead-shaped hole geometry. Experimental results demonstrate that the proposed hole geometry improves the film effectiveness on both suction and pressure surface of a generic turbine airfoil. Film effectiveness data for a row of the holes are compared to that of fan-shaped holes at the same inclination angle of 35 deg to the surface on a large-scale airfoil model at engine representative Reynolds number and Mach number in a high-speed tunnel with moderately elevated temperature mainstream flow. The film effectiveness data are collected using pressure-sensitive paint. Numerical results show that the coolant film with the proposed hole geometry remains well attached to the surface and diffuses in the lateral direction in comparison with the conventional laidback fan-shaped holes for coolant to mainstream blowing ratios of 0.6–3.5.
Дисертації з теми "Film effectiveness"
1
Collins, Alan, and Jen Snowball. "The effectiveness and impacts of subsidies to film industries." South African Cultural Observatory (SACO), 2016. http://hdl.handle.net/10962/68511.
Повний текст джерелаАнотація:
Publisher versionConference paper presented at the South African Cultural Observatory, First National Conference: Counting Culture, The Cultural and Creative Industries in National and International Context, 16-17 May 2016, The Boardwalk International Convention Centre, Nelson Mandela Bay.
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Varvel, Trent Alan. "Shaped hole effects on film cooling effectiveness and a comparison of multiple effectiveness measurement techniques." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1524.
Повний текст джерелаАнотація:
This experimental study consists of two parts. For the first part, the film cooling effectiveness for a single row of seven cylindrical holes with a compound angle is measured on a flat surface using five different measurement techniques: steady-state liquid crystal thermography, transient liquid crystal thermography, pressure sensitive paint (PSP), thermocouples, and infrared thermography. A comparison of the film cooling effectiveness from each of the measurement techniques is presented. All methods show a good comparison, especially for the higher blowing ratios. The PSP technique shows the most accurate measurements and has more advantages for measuring film cooling effectiveness. Also, the effect of blowing ratio on the film cooling effectiveness is investigated for each of the measurement techniques.
The second part of the study investigates the effect of hole geometries on the film cooling effectiveness using pressure sensitive paint. Nitrogen is injected as the coolant air so that the oxygen concentration levels can be obtained for the test surface. The film effectiveness is then obtained by the mass transfer analogy. Five total hole geometries are tested: fan-shaped laidback with a compound angle, fan-shaped laidback with a simple angle, a conical configuration with a compound angle, a conical configuration with a simple angle, and the reference geometry (cylindrical holes) used in part one. The effect of blowing ratio on film cooling effectiveness is presented for each hole geometry. The spanwise averaged effectiveness for each geometry is also presented to compare the geometry effect on film cooling effectiveness. The geometry of the holes has little effect on the effectiveness at low blowing ratios. The laterally expanded holes show improved effectiveness at higher blowing ratios.
All experiments are performed in a low speed wind tunnel with a mainstream velocity of 34 m/s. The coolant air is injected through the coolant holes at four different coolant-to-mainstream velocity ratios: 0.3, 0.6, 1.2, and 1.8.
3
Marsh, Jan H. "Development of an experimental setup for the study of film pulsation effects on film cooling effectiveness." Honors in the Major Thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1111.
Повний текст джерелаАнотація:
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Aerospace Engineering
4
Gao, Zhihong. "Experimental investigation of film cooling effectiveness on gas turbine blades." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1557.
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Li, Ke. "Experimental Study of Heat Transfer Coefficient and Film Cooling Effectiveness." Thesis, KTH, Energiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-249061.
Повний текст джерелаАнотація:
This thesis investigates the possibility to evaluate the film cooling thermal performance on flat plate using Thermochromic Liquid Crystal. After an introduction of the basic concept and background of gas turbine blades film cooling and Thermochromic Liquid Crystal, a thorough explanation of four methods is presented. Dimensional or similarity analysis is implemented to build relationship between real engine and laboratory model. Also, the Reynolds number and Blowing ratio are the fundamental of test object design and TLC selection. This study illustrated the layout of the test rig and corresponding setups, and the following part explains the data collection system and image processing MATLAB script which is vital for the success of data extraction. The least square method is applied to figure time-series optimal solution in solver. All the experiments are conducted at near room temperature as opposed to the extremely high gas turbine exhausted gas, including two calibration test and one heat transfer experiment. The heat transfer coefficient and film cooling effectiveness are the target objective through the entire project. By comparison with a similar experiment in a literature, the outcomes partially validated the film cooling performance under the pre-set flow and thermal condition and the Liquid Crystal thermography technique is proved to be a trustworthy method to mapping heat transfer surface.Denna avhandling undersöker möjligheten att utvärdera filmkylningens termiska prestanda på plan platta med användning av Termokromisk Flytande Kristall (TLC). Efter en introduktion av grundkonceptet och bakgrunden till gasturbinbladens filmkylning och termokromisk flytande kristall presenteras en grundlig förklaring av fyra metoder. Dimensionell eller likhetsanalys implementeras för att bygga upp förhållandet mellan verklig motor och laboratoriemodell. Reynoldstalet och blåsningsförhållandet (blowing ratio) är också grunden för testobjektdesign och TLC-val. Denna studie illustrerade provriggens layout och tillhörande inställningar. I följande del förklaras datainsamlingssystemet och bildbehandling, MATLABTM-skriptet som är avgörande för framgång med datautvärdering. Den minsta kvadratiska metoden tillämpas för att hitta tidsseriens optimala lösning i lösaren. Alla experiment utförs vid nära rumstemperatur i motsats till den höga temperature på gasturbingasen, inklusive två kalibreringstest och ett värmeöverföringsexperiment. Värmeöverföringskoefficienten och filmkylningseffektiviteten är målmålet genom hela projektet. Resultaten validerade partiellt filmkylningens prestanda under det förinställda flödet och det termiska tillståndet. Liquid Crystal-termografitekniken har visat sig vara en pålitlig metod för att kartlägga värmeöverföringsytan jämfört med ett liknande experiment i den öppna litteraturen.
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Aghasi, Paul P. "Dependence of Film Cooling Effectiveness on 3D Printed Cooling Holes." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1458893416.
Повний текст джерела
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Rodriguez, Sylvette. "EFFECT OF PRESSURE GRADIENT AND WAKE ON ENDWALL FILM COOLING EFFECTIVENESS." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2940.
Повний текст джерелаАнотація:
Endwall film cooling is a necessity in modern gas turbines for safe and reliable operation. Performance of endwall film cooling is strongly influenced by the hot gas flow field, among other factors. For example, aerodynamic design determines secondary flow vortices such as passage vortices and corner vortices in the endwall region. Moreover blockage presented by the leading edge of the airfoil subjects the incoming flow to a stagnating pressure gradient leading to roll-up of the approaching boundary layer and horseshoe vortices. In addition, for a number of heavy frame power generation gas turbines that use cannular combustors, the hot and turbulent gases exiting from the combustor are delivered to the first stage vane through transition ducts. Wakes induced by walls separating adjacent transition ducts located upstream of first row vanes also influence the entering main gas flow field. Furthermore, as hot gas enters vane passages, it accelerates around the vane airfoils. This flow acceleration causes significant streamline curvature and impacts lateral spreading endwall coolant films. Thus endwall flow field, especially those in utility gas turbines with cannular combustors, is quite complicated in the presence of vortices, wakes and strong favorable pressure gradient with resulting flow acceleration. These flow features can seriously impact film cooling performance and make difficult the prediction of film cooling in endwall. This study investigates endwall film cooling under the influence of pressure gradient effects due to stagnation region of an axisymmetric airfoil and in mainstream favorable pressure gradient. It also investigates the impact of wake on endwall film cooling near the stagnation region of an airfoil. The investigation consists of experimental testing and numerical simulation. Endwall film cooling effectiveness is investigated near the stagnation region on an airfoil by placing an axisymmetric airfoil downstream of a single row of inclined cylindrical holes. The holes are inclined at 35° with a length-to-diameter ratio of 7.5 and pitch-to-diameter ratio of 3. The ratio of leading edge radius to hole diameter and the ratio of maximum airfoil thickness to hole diameter are 6 and 20 respectively. The distance of the leading edge of the airfoil is varied along the streamwise direction to simulate the different film cooling rows preceding the leading edge of the airfoil. Wake effects are induced by placing a rectangular plate upstream of the injection point where the ratio of plate thickness to hole diameter is 6.4, and its distance is also varied to investigate the impact of strong and mild wake on endwall film cooling effectiveness. Blowing ratio ranged from 0.5 to 1.5. Film cooling effectiveness is also investigated under the presence of mainstream pressure gradient with converging main flow streamlines. The streamwise pressure distribution is attained by placing side inserts into the mainstream. The results are presented for five holes of staggered inclined cylindrical holes. The inclination angle is 30° and the tests were conducted at two Reynolds number, 5000 and 8000. Numerical analysis is employed to aid the understanding of the mainstream and coolant flow interaction. The solution of the computational domain is performed using FLUENT software package from Fluent, Inc. The use of second order schemes were used in this study to provide the highest accuracy available. This study employed the Realizable κ-ε model with enhance wall treatment for all its cases. Endwall temperature distribution is measured using Temperature Sensitive Paint (TSP) technique and film cooling effectiveness is calculated from the measurements and compared against numerical predictions. Results show that the characteristics of average film effectiveness near the stagnation region do not change drastically. However, as the blowing ratio is increased jet to jet interaction is enhanced due to higher jet spreading resulting in higher jet coverage. In the presence of wake, mixing of the jet with the mainstream is enhanced particularly for low M. The velocity deficit created by the wake forms a pair of vortices offset from the wake centerline. These vortices lift the jet off the wall promoting the interaction of the jet with the mainstream resulting in a lower effectiveness. The jet interaction with the mainstream causes the jet to lose its cooling capabilities more rapidly which leads to a more sudden decay in film effectiveness. When film is discharged into accelerating main flow with converging streamlines, row-to-row coolant flow rate is not uniform leading to varying blowing ratios and cooling performance. Jet to jet interaction is reduced and jet lift off is observed for rows with high blowing ratio resulting in lower effectiveness.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD
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Ahn, Jaeyong. "Film cooling effectiveness measurements on rotating and non-rotating turbine components." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4664.
Повний текст джерелаАнотація:
Detailed film cooling effectiveness distributions were measured on the stationary
blade tip and on the leading edge region of a rotating blade using a Pressure Sensitive
Paint technique. Air and nitrogen gas were used as the film cooling gases and the
oxygen concentration distribution for each case was measured. The film cooling
effectiveness information was obtained from the difference of the oxygen concentration
between air and nitrogen gas cases by applying the mass transfer analogy. In the case of
the stationary blade tip, plane tip and squealer tip blades were used while the film
cooling holes were located (a) along the camber line on the tip or (b) along the span of
the pressure side. The average blowing ratio of the cooling gas was controlled to be 0.5,
1.0, and 2.0. Tests were conducted in a five-bladed linear cascade with a blow down
facility. The free stream Reynolds number, based on the axial chord length and the exit
velocity, was 1,100,000 and the inlet and the exit Mach number were 0.25 and 0.59,
respectively. Turbulence intensity level at the cascade inlet was 9.7%. All
measurements were made at three different tip gap clearances of 1%, 1.5%, and 2.5% of
blade span. Results show that the locations of the film cooling holes and the presence
of squealer have significant effects on surface static pressure and film-cooling effectiveness. Same technique was applied to the rotating turbine blade leading edge
region. Tests were conducted on the first stage rotor of a 3-stage axial turbine. The
Reynolds number based on the axial chord length and the exit velocity was 200,000 and
the total to exit pressure ratio was 1.12 for the first rotor. The effects of the rotational
speed and the blowing ratio were studied. The rotational speed was controlled to be
2400, 2550, and 3000 rpm and the blowing ratio was 0.5, 1.0, and 2.0. Two different
film cooling hole geometries were used; 2-row and 3-row film cooling holes. Results
show that the rotational speed changes the directions of the coolant flows. Blowing
ratio also changes the distributions of the coolant flows. The results of this study will
be helpful in understanding the physical phenomena regarding the film injection and
designing more efficient turbine blades.
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Zuniga, Humberto. "STUDY OF FILM COOLING EFFECTIVENESS: CONICAL, TRENCHED AND ASYMMETRICAL SHAPED HOLES." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2239.
Повний текст джерелаАнотація:
Film cooling is a technique whereby air from the compressor stage of a gas turbine engine is diverted for cooling purposes to parts, such as the turbine stage, that operate at very high temperatures. Cooling arrangements include impingement jets, finned, ribbed and turbulated channels, and rows of film cooling holes, all of which over the years have become progressively more complex. This costly, but necessary complexity is a result of the industry's push to run engines at increasingly higher turbine inlet temperatures. Higher temperatures mean higher efficiency, but they also mean that the turbine first stage operates hundreds of degrees Kelvin above the melting point of the metal core of the vanes and blades. Existing cooling technology and materials make it possible to protect these parts and allow them to function for extended periods of time--but this comes at a price: the compressed air that is used for cooling represents a considerable penalty in overall turbine efficiency. The aim of current cooling research is threefold: to improve the protection of components from extreme fluxes in order to extend the life of the parts; to increase the inlet turbine operating temperature; and to reduce the amount of air that is diverted from the compressor for cooling. Current film cooling schemes consist of forcing air through carefully machined holes on a part and ejecting it at an angle with the intent of cooling that part by blanketing the surface downstream of the point of ejection. The last major development in the field has been the use of expanded hole exits, which reduce coolant momentum and allow for greater surface coverage. Researchers and designers are continuously looking for novel geometries and arrangements that would increase the level of protection or maintain it while using less coolant.
It was found that the performance of fan-shaped holes inside trenches is actually diminished by the presence of the trench. It is obvious, since the fan diffuses the flow, reducing the momentum of the coolant; the addition of the trench further slows the flow down. This, in turn, leads to the quicker ingestion of the main flow by the jets resulting in lower effectiveness. The next part of the study consisted of systematically increasing the depth of the trench for the fan-shaped holes. The purpose of this was to quantify the effect of the trench on the film cooling effectiveness. It was found that the presence of the trench significantly reduces the film effectiveness, especially for the deeper cases. At the higher blowing ratios, the overall performance of the fans collapses to the same value signifying insensitivity to the blowing ratio. A recent study suggests that having a compound angle could reduce the protective effect of the film due to the elevated interaction between the non-co-flowing coolant jet and the mainstream. Although it has been suggested that a non-symmetric lateral diffusion could mitigate the ill effects of having a compound angle, little has been understood on the effect this non-symmetry has on film cooling effectiveness. The last part of this study investigates the effect of non-symmetric lateral diffusion on film cooling effectiveness by systematically varying one side of a fan-shaped hole. For this part of the study, one of the lateral angles of diffusion of a fan-shaped hole was changed from 5° to 13°, while the other side was kept at 7°. It was found that a lower angle of diffusion hurts performance, while a larger diffusion angle improves it. However, the more significant result was that the jet seemed to be slightly turning. This dissertation investigates such novel methods which one day may include combinations of cylindrical and fan-shaped holes embedded inside trenches, conical holes, or even rows of asymmetric fan-shaped holes. The review of current literature reveals that very few investigations have been done on film cooling effectiveness for uniformly diffusing conical holes. They have been treated as a sort of side novelty since industrial partners often say they are hard to manufacture. To extend our understanding of effectiveness of conical holes, the present study investigates the effect of increasing diffusion angle, as well as the effect of adding a cylindrical entrance length to a conical hole. The measurements were made in the form of film cooling effectiveness and the technique used was temperature sensitive paint. Eight different conical geometries were tested in the form of coupons with rows of holes. The geometry of the holes changed from pure cylindrical holes, a 0° cylindrical baseline, to an 8° pure cone. The coupons were tested in a closed loop wind tunnel at blowing ratios varying from 0.5 to 1.5, and the coolant employed was nitrogen gas. Results indicate that the larger conical holes do, in fact offer appropriate protection and that the holes with the higher expansion angles perform similar to fan-shaped baseline holes, even at the higher blower ratios. The study was also extended to two other plates in which the conical hole was preceded by a cylindrical entry length. The performance of the conical holes improves as a result of the entry length and this is seen at the higher blowing ratios in the form of a delay in the onset of jet detachment. The results of this study show that conical expanding holes are a viable geometry and that their manufacturing can be made easier with a cylindrical entry length, at the same time improving the performance of these holes.
This suggests that the jets actually have two regions: one region with reduced momentum, ideal for protecting a large area downstream of the point of injection; and another region with more integrity which could withstand more aggressive main flow conditions. A further study should be conducted for this geometry at compound angles with the main flow to test this theory. The studies conducted show that the temperature sensitive paint technique can be used to study the performance of film cooling holes for various geometries. The studies also show the film cooling performance of novel geometries and explain why, in some cases, such new arrangements are desirable, and in others, how they can hurt performance. The studies also point in the direction of further investigations in order to advance cooling technology to more effective applications and reduced coolant consumption, the main goal of applied turbine cooling research.
Trench cooling consists of having film cooling holes embedded inside a gap, commonly called a trench. The walls of this gap are commonly vertical with respect to the direction of the main flow and are directly in the path of the coolant. The coolant hits the downstream trench wall which forces it to spread laterally, resulting in more even film coverage downstream than that of regular holes flush with the surface. Recent literature has focused on the effect that trenching has on cylindrical cooling holes only. While the results indicate that trenches are an exciting, promising new geometry derived from the refurbishing process of thermal barrier ceramic coatings, not all the parameters affecting film cooling have been investigated relating to trenched holes. For example, nothing has been said about how far apart holes inside the trench will need to be placed for them to stop interacting. Nothing has been said about shaped holes inside a trench, either. This dissertation explores the extent to which trenching is useful by expanding the PI/D from 4 to 12 for rows of round and fan holes. In addition the effect that trenching has on fan-shaped holes is studied by systematically increasing the trench depth. Values of local, laterally-averaged and spatially-averaged film cooling effectiveness are reported. It is found that placing the cylinders inside the trench and doubling the distance between the holes provides better performance than the cylindrical, non-trenched baseline, especially at the higher blowing ratios, M [greater than] 1.0. At these higher coolant flow rates, the regular cylindrical jets show detachment, while those in the trench do not. They, in fact perform very well. The importance of this finding implies that the number of holes, and coolant, can be cut in half while still improving performance over regular holes. The trenched cylindrical holes did not, however, perform like the fan shaped holes.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering PhD
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Chen, Amber Marie. "Developing and Studying the Effectiveness of EFR Annotations for Chinese Language Learners." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2299.
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This project is intended to take the film To Live, directed by Zhang Yimou, and apply the Electronic Film Review (EFR) approach to it in a Chinese as a Foreign Language (CFL) setting. The Electronic Film Review project, developed by Alan K. Melby, is aimed at providing a superior language learning experience for Americans learning Chinese. Using feature films as a teaching tool has been found to stimulate and motivate students to achieve higher language levels, but in order for optimal learning to occur the material must be challenging yet accessible to the student. Most feature films, by themselves, are too advanced for the average language learner. The EFR approach provides annotations designed specifically for the feature film with the language learner in mind. These annotations can include access to vocabulary helps, grammar and cultural notes in order to bridge the gap between the learner and the film. It does not alter the film itself. This approach has been used with ESL students (English annotations), French language learners, and with Korean ESL learners (Korean annotations), but has not been developed for students learning Chinese. The purpose of this project is not only to apply the technology of the Electronic Film Review program to a Chinese film for the purpose of aiding Chinese language learners, but also to critique whether or not the tool is effective in helping students to gain better listening comprehensions skills and therefore ultimately better language skills. Previous studies have not shown clear results on this issue. This thesis will briefly review what the EFR project is and how it has been used with other films and languages as well as the findings up to this point. Then it will look at the effects of annotations on several aspects of listening comprehension as well as student preferences and reactions. It will then evaluate the results collectively to determine whether students watching the film without the help of EFR annotations show differing levels of listening comprehension achievement when compared with those using the EFR tools. Suggestions will be made for further improvements.
Книги з теми "Film effectiveness"
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L, Rigby D., and NASA Glenn Research Center, eds. A numerical analysis of heat transfer and effectiveness on film cooled turbine blade tip models. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.
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Pratsides, Irene. A study of the effectiveness of an educational film series to change the attitudes of pupils to science. London: North East London Polytechnic, 1985.
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3
Wigle, James Michael. Heat transfer, adiabatic effectiveness and injectant distribution downstream of single and double rows of film-cooling holes with compound angles. Monterey, Calif: Naval Postgraduate School, 1991.
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Ciriello, Salvatore. Heat transfer, adiabatic effectiveness and injectant distributions downstream of single and double rows of film-cooling holes with simple and compound angles. Monterey, Calif: Naval Postgraduate School, 1991.
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Jackson, Stephen Mark. Heat transfer, adiabatic effectiveness and injectant distributions downstream of single rows and two staggered rows of film-cooling holes with simple and compound angles. Monterey, Calif: Naval Postgraduate School, 1991.
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Daniel, Gulati, and Segovia W. Oliver, eds. Passion & purpose: Stories from the best and brightest young business leaders. Boston, Mass: Harvard Business Review Press, 2012.
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Petersen, Stephen R. A user's guide to the Federal Building Life-Cycle Cost (FBLCC) computer program. Gaithersburg, MD: U.S. Dept. of Commerce, National Bureau of Standards, 1986.
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Fennell, Karen. To e stablish suitable effectiveness criteria for formally managing the performance of supervisors and managers within the organisation of Safeway. (s.l: The Author), 2004.
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Puri, Praveen. Advanced UNIX shell scripting: How to reduce your labor and increase your effectiveness through mastery of Unix shell scripting and Awk programming. S. l: P. Puri, 2013.
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Barnes, Jennifer. Review of MicroBENCOST for WSDOT Mobility. [Olympia, Wash: Washington State Dept. of Transportation, 1998.
Знайти повний текст джерелаЧастини книг з теми "Film effectiveness"
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Zhang, Ling, Tingting Guo, Shaohua Li, and Jianhong Liu. "Effects of Jet Geometries on Film-cooling Effectiveness." In Challenges of Power Engineering and Environment, 1357–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-76694-0_255.
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Terzić, Anja, and Lato Pezo. "Assessment of the Effectiveness of Producing Mineral Fillers via Pulverization for Ceramic Coating Materials." In Photoenergy and Thin Film Materials, 537–62. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2019. http://dx.doi.org/10.1002/9781119580546.ch13.
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Suresh, Batchu, Resham D. Khade, V. Kesavan, and D. Kishore Prasad. "Investigation for the Improvement of Film Cooling Effectiveness of Effusion Cooling Holes." In Proceedings of the National Aerospace Propulsion Conference, 171–84. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5039-3_10.
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Shu, Z., C. Dai, and J. Mi. "Numerical Simulations on Film Cooling Effectiveness from Two Staggered Rows of Coolant Jets." In Fluid-Structure-Sound Interactions and Control, 143–48. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-7542-1_22.
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Kai, Cao, Kairang Wang, and Changwen Liu. "Shielding Effectiveness Improvement Method of Optoelectronic Instrumental Windows Utilizing Transparent Mesh PET Film." In Wireless and Satellite Systems, 656–60. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-19156-6_62.
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Donshik, Peter C., J. Daniel Nelson, Mark Abelson, James P. McCulley, Cliff Beasley, and Robert A. Laibovitz. "Effectiveness of Bion Tears, Cellufresh, Aquasite, and Refresh Plus for Moderate to Severe Dry Eye." In Lacrimal Gland, Tear Film, and Dry Eye Syndromes 2, 753–60. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4615-5359-5_106.
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Peter, Johannes M. F., and Markus J. Kloker. "Numerical Simulation of Film Cooling in Supersonic Flow." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 79–95. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_5.
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Abstract High-order direct numerical simulations of film cooling by tangentially blowing cool helium at supersonic speeds into a hot turbulent boundary-layer flow of steam (gaseous H2O) at a free stream Mach number of 3.3 are presented. The stagnation temperature of the hot gas is much larger than that of the coolant flow, which is injected from a vertical slot of height s in a backward-facing step. The influence of the coolant mass flow rate is investigated by varying the blowing ratio F or the injection height s at kept cooling-gas temperature and Mach number. A variation of the coolant Mach number shows no significant influence. In the canonical baseline cases all walls are treated as adiabatic, and the investigation of a strongly cooled wall up to the blowing position, resembling regenerative wall cooling present in a rocket engine, shows a strong influence on the flow field. No significant influence of the lip thickness on the cooling performance is found. Cooling correlations are examined, and a cooling-effectiveness comparison between tangential and wall-normal blowing is performed.
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Mohammed Ibrahim, S., R. Sriram, S. Chattopadhyay, G. Jagadeesh, and K. P. J. Reddy. "Effectiveness of Film Cooling over Large Angle Blunt Cones in High Speed Carbon Dioxide Flows." In 29th International Symposium on Shock Waves 1, 581–86. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-16835-7_92.
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Chorafas, Dimitris N. "A Survival Strategy: Reinventing the Firm." In Rating Management's Effectiveness, 76–99. London: Palgrave Macmillan UK, 2004. http://dx.doi.org/10.1057/9780230005907_4.
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Lécureuil, Christophe, and Simon Ward. "New Models of Large Firm Collective Action." In The Effectiveness of EU Business Associations, 126–30. London: Palgrave Macmillan UK, 2002. http://dx.doi.org/10.1057/9780230629370_13.
Повний текст джерелаТези доповідей конференцій з теми "Film effectiveness"
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Mathison, R. M., M. G. Dunn, M. M. Weaver, and A. Dushko. "Measurement of Air Film Damping Effectiveness." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53057.
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Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the Two-Stripe Mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the ressonant frequencies lower.
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El-Gabry, Lamyaa A., and Richard B. Rivir. "Effect of Pulsed Film Cooling on Leading Edge Film Effectiveness." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37354.
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Detailed film effectiveness measurements have been made on a cylindrical leading edge surface for steady and pulsating flow. The film hole is off-centered by 21.5° from the centerline and angled 20° to the surface and 90° from the stream wise direction. Two jet-to-cross-flow velocity ratios have been considered: VR = 1 and 2 which correspond to blowing ratio of 1 and 2, respectively. The pulsating frequency is 10 Hz and the duty cycle is 50%. Comparisons between film effectiveness with a pulsating film and a continuous film show that for the same blowing ratio, the effectiveness of the film drops by a factor of 2 when the flow is pulsed. Hotwire measurements are made to characterize the pulsating velocity waveform at the exit of the film exit and verify the integrity of the pulse. The variation in the measured surface adiabatic wall temperature over the pulsing duration is very small suggesting a large thermal inertia that keeps the wall surface largely unaffected by the time scale of the pulsations; this holds true for both blowing ratios tested.
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Yusop, Nadiahnor Md, Gordon E. Andrews, Derek B. Ingham, I. M. Khalifa, Mike C. Mkpadi, and Mohammed Pourkashanian. "Predictions of Adiabatic Film Cooling Effectiveness for Effusion Film Cooling." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27467.
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This paper presents computational predictions of adiabatic film cooling effectiveness for effusion cooling systems with 90° and 30° holes. Predictions are performed for a range of coolant injection mass flow rates per unit surface area, G, of 0.1kg/sm2 - 1.6 kg/sm2 for 90° holes with constant pitch-to-diameter ratio of X/D = 11 and 10 rows of holes and for 30° inclined holes with X/D = 11 and 15 rows of holes over a 152mm surface length. The computational works performed are steady-state and the turbulent governing equations are solved by a control-volume-based finite difference method with second-order upwind scheme and the k-epsilon turbulence model. The velocity and pressure terms of momentum equations are solved by the SIMPLE method. The CFD prediction were validated by comparing the predictions with literature data for single rows of inclined holes and then applied to effusion cooling. The predictions included the use of a tracer gas in the coolant, which was used to predict the mixing of the coolant with the hot mainstream gases. Also the surface distribution of the tracer gas was a direct prediction of the cooling effectiveness. The mixing of coolant with the mainstream was studied and boundary layer temperature and coolant mixing profiles were predicted. These were compared with temperature measurement in a hot effusion cooling test rig.
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Natsui, Greg, Zachary Little, Jay Kapat, Anthony Socotch, Anquan Wang, and Jason E. Dees. "Adiabatic Film Cooling Effectiveness Measurements Throughout Multi-Row Film Cooling Arrays." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56183.
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Adiabatic film cooling effectiveness measurements are obtained using pressure-sensitive paint (PSP) on a flat film cooled surface. The effects of blowing ratio and hole spacing are investigated for four multi-row arrays comprised of 8 rows containing 52 holes of 3.8 mm diameter with 20° inclination angles and hole length-to-diameter ratio of 11.2. The four arrays investigated have two different hole-to-hole spacings composed of cylindrical and diffuser holes. For the first case, lateral and streamwise pitches are 7.5 times the diameter. For the second case, pitch-to-diameter ratio is 14 in lateral direction and 10 in the streamwise direction. The holes are in a staggered arrangement. Adiabatic effectiveness measurements are taken for a blowing ratio range of 0.3 to 1.2 and a density ratio of 1.5, with CO2 injected as the coolant. A thorough boundary layer analysis is presented, and data was taken using hotwire anemometry with air injection, with boundary layer and turbulence measurements taken at multiple locations in order to characterize the boundary layer. Local effectiveness, laterally averaged effectiveness, boundary layer thickness, momentum thickness, turbulence intensity and turbulence length scale are presented. For the cylindrical holes, at the first row of injection, the film jets are still attached at a blowing ratio of 0.3. By a blowing ratio of 0.5, the jet is observed to lift off, and then impinge back onto the test surface. At a blowing ratio of 1.2, the jets lift off, but reattach much further downstream, spreading the coolant further along the test surface. A thorough uncertainty analysis has been conducted in order to fully understand the presented measurements and any shortcomings of the measurement technique. The maximum uncertainty of effectiveness and blowing ratio is 0.02 counts of effectiveness and 3 percent respectively.
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Lewis, Scott, Brett Barker, Jeffrey P. Bons, Weiguo Ai, and Thomas H. Fletcher. "Film Cooling Effectiveness and Heat Transfer Near Deposit-Laden Film Holes." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59567.
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Experiments were conducted to determine the impact of synfuel deposits on film cooling effectiveness and heat transfer. Scaled up models were made of synfuel deposits formed on film-cooled turbine blade coupons exposed to accelerated deposition. Three distinct deposition patterns were modeled: a large deposition pattern (max deposit peak ≅ 2 hole diameters) located exclusively upstream of the holes, a large deposition pattern (max deposit peak ≅ 1.25 hole diameters) extending downstream between the cooling holes, and a small deposition pattern (max deposit peak ≅ 0.75 hole diameter) also extending downstream between the cooling holes. The models featured cylindrical holes inclined at 30 degrees to the surface and aligned with the primary flow direction. The spacing of the holes were 3, 3.35, and 4.5 hole diameters respectively. Flat models with the same film cooling hole geometry and spacing were used for comparison. The models were tested using blowing ratios of 0.5–2 with a turbulent approach boundary layer and 0.5% freestream turbulence. The density ratio was approximately 1.1 and the primary flow Reynolds number at the film cooling row location was 300,000. An infrared camera was used to obtain the film cooling effectiveness from steady state tests and surface convective heat transfer coefficients using transient tests. The model with upstream deposition caused the primary flow to lift off the surface over the roughness peaks and allowed the coolant to stay attached to the model. Increasing the blowing ratio from 0.5 to 2 only expanded the region that the coolant could reach and improved the cooling effectiveness. Though the heat transfer coefficient also increased at high blowing ratios, the net heat flux ratio was still less than unity, indicating film cooling benefit. For the two models with deposition between the cooling holes, the free stream air was forced into the valleys in line with the coolant holes and degraded area-averaged coolant performance at lower blowing ratios. It is concluded that the film cooling effectiveness is highest when deposition is limited to upstream of the cooling holes. When accounting for the insulating effect of the deposits between the film holes, even the panels with deposits downstream of the film holes can yield a net decrease in heat flux for some cases.
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Okita, Yoji, and Masakazu Nishiura. "Film Effectiveness Performance of an Arrowhead-Shaped Film Cooling Hole Geometry." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90108.
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This paper presents the first experimental and numerical work of film effectiveness performance for a novel film cooling method with an arrowhead-shaped hole geometry. Experimental results demonstrate that the proposed hole geometry improves the film effectiveness on both suction and pressure surface of a generic turbine airfoil. Film effectiveness data for a row of the holes are compared with that of fan-shaped holes at the same inclination angle of 35° to the surface on a large-scale airfoil model at engine representative Reynolds number and Mach number in a high speed tunnel with moderately elevated temperature mainstream flow. The film effectiveness data are collected using pressure sensitive paint (PSP). Numerical results show that the coolant film with the proposed hole geometry remains well attached to the surface and diffuses in the lateral direction in comparison with the conventional laidback fan-shaped holes for coolant to mainstream blowing ratios of 0.6 to 3.5.
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Vighneswara Rao, K., Jong S. Liu, Daniel C. Crites, Luis A. Tapia, Malak F. Malak, G. Sujatha, and S. Balamurugan. "Enhanced Film Cooling Effectiveness With Surface Trenches." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94530.
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In this study, cylindrical and fan shaped film cooling holes are evaluated on the blade surface numerically, using the Computational Fluid Dynamics (CFD) tool ANSYS-CFX, with the objective of improving cooling effectiveness by understanding the flow pattern at the cooling hole exit. The coolant flow rates are adjusted for blowing ratios of 0.5, 1.0 & 1.5 (momentum flux ratios of 0.125, 0.5 & 1.125 respectively). The density ratio is maintained at 2.0. New shaped holes viz. straight, concave and convex trench holes are introduced and are evaluated under similar operating conditions. Results are presented in terms of surface temperatures and adiabatic effectiveness at three different blowing ratios for the different film cooling hole shapes analyzed. Comparison is made with reference to the fan shaped film cooling hole to bring out relative merits of different shapes. The new trench holes improved the film cooling effectiveness by allowing more residence time for coolant to spread laterally while directing smoothly onto the airfoil surface. While convex trench improved the centre-line effectiveness, straight trench improved the laterally-averaged and overall effectiveness at all blowing ratios. Concave trench improved the effectiveness at blowing ratios 0.5 and 1.0.
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Derrar, M., J. Nagler, and W. W. Koschel. "Cooling Effectiveness on Film Cooled Turbine Blades." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/htd-24319.
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Abstract This paper presents experiments on the cooling effectiveness obtained for two different injection locations on the suction side of a turbine blade at transonic flow conditions. Previous results of a computational analysis and flow visualization indicated that a separation bubble is present on the suction side at a location x/L = 0.43 and the location x/L = 0.575 corresponds to a shock-boundary interaction zone [9]. The scientific interest is primarily focused on the realization of high film cooling efficiencies and its relevant parameters under these flow conditions. Streamwise aligned as well as inclined angled film coolant hole configurations have been investigated for each location. Due to the high number of interacting parameters the experimental simulation of turbine blade film cooling is extremely complex, which can only be solved by a simultaneous modeling using the experimentally measured results. Test rig, instrumentation and data analysis are described in detail. The goal of the investigations is to determine the optimum location of the film coolant injection.
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Rhee, Dong Ho, Youn Seok Lee, and Hyung Hee Cho. "Film Cooling Effectiveness and Heat Transfer of Rectangular-Shaped Film Cooling Holes." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30168.
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An experimental study has been conducted to measure the local film-cooling effectiveness and the heat transfer coefficient for a single row of rectangular-shaped holes. The holes have a 35° inclination angle with 3 hole diameter spacing of rectangular cross-sections. Four different cooling hole shapes such as a straight rectangular hole, a rectangular hole with laterally expanded exit, a circular hole and a two-dimensional slot are tested. The rectangular cross-section has the aspect ratio of 2 at the hole inlet with the hydraulic diameter of 10 mm. The area ratio of the exit to the hole inlet is 1.8 for the rectangular hole with expanded exit, which is similar to a two-dimensional slot. A thermochromic liquid crystals technique is applied to determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. Both film cooling effectiveness and heat transfer coefficient are measured for various blowing rates and compared with the results of the cylindrical holes and the two-dimensional slot. The flow patterns inside and downstream of holes are calculated numerically by a commercial package. The results show that the rectangular holes provide better performance than the cylindrical holes. For the rectangular holes with laterally expanded exit, the penetration of jet is reduced significantly, and the higher and more uniform cooling performance is obtained even at relatively high blowing rates. The reason is that the rectangular hole with expanded exit reduces momentum of coolant and promotes the lateral spreading like a two-dimensional slot.
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Kim, Sun-min, Ki-Don Lee, and Kwang-Yong Kim. "Numerical Study on Film-Cooling Effectiveness for Various Film-Cooling Hole Schemes." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-22003.
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Film-cooling has been widely used as the important alternative to protect the turbine blade. Since the film-cooling hole geometry is one of the most influential parameters for film-cooling performance, various film-cooling hole schemes have been developed to increase cooling performance for the past few decades. In the present work, numerical analysis has been performed to investigate and to compare the film-cooling performance of various film-cooling hole schemes such as fan-shaped, crescent, louver, and dumbbell holes. For analyzes of the turbulent flow and film-cooling, three-dimensional Reynolds-averaged Navier-Stokes analysis has been performed with shear stress transport turbulence model. The validation of numerical results has been performed in comparison with experimental data. The flow characteristics and film-cooling performance for each hole shape have been investigated and evaluated in terms of local- and averaged film-cooling effectivenesses.
Звіти організацій з теми "Film effectiveness"
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Mclntyre, J. F., R. K. Conrad, and A. Sheetz. Effectiveness of Thin Film Fluoropolymers as Protective Coatings in Marine Environments,. Fort Belvoir, VA: Defense Technical Information Center, June 1994. http://dx.doi.org/10.21236/ada331020.
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Benavente, José Miguel, and Pluvia Zuñiga. The Effectiveness of Innovation Policy and the Moderating Role of Market Competition: Evidence from Latin American Firms. Inter-American Development Bank, September 2021. http://dx.doi.org/10.18235/0003655.
Повний текст джерелаАнотація:
This paper evaluates whether market competition matters for the effectiveness of innovation policies. Using data for manufacturing firms in Chile and Peru, we implement propensity matching techniques combined with differences-in-differences estimation to evaluate the impact of innovation subsidies on the post-treatment innovation investment effort of firms and test whether such impact differs according to the intensity of competition. We corroborate the existence of crowding-in effects in beneficiaries when compared to a control group of untreated firms. The subsidy impact is found either only significant in highly competitive sectors or larger in more competition-intensive industries -compared to low competition ones. Thus, we confirm that market competition plays a moderating role in the effectiveness of innovation policies to stimulate firm innovation investment. The results are robust to different matching and estimation methods and suggest, therefore, the importance of considering market contexts in the design of innovation policies.
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Goyet, C. The Role of Hydrate Films in the Effectiveness of Direct CO2 Injection as an Ocean Carbon Sequestration Strategy. Office of Scientific and Technical Information (OSTI), May 2004. http://dx.doi.org/10.2172/15014229.
Повний текст джерела
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Garcia, Lyan, James Rowland, and Jeb Tingle. Evaluation of geocell-reinforced backfill for airfield pavement repair. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42550.
Повний текст джерелаАнотація:
After an airfield has been attacked, temporary airfield pavement repairs should be accomplished quickly to restore flight operations. Often, the repairs are made with inadequate materials and insufficient manpower due to limited available resources. Legacy airfield damage repair (ADR) methods for repairing bomb damage consist of using bomb damage debris to fill the crater, followed by placement of crushed stone or rapid-setting flowable fill backfill with a foreign object debris (FOD) cover. While these backfill methods have provided successful results, they are heavily dependent on specific material and equipment resources that are not always readily available. Under emergency conditions, it is desirable to reduce the logistical burden while providing a suitable repair, especially in areas with weak subgrades. Geocells are cellular confinement systems of interconnected cells that can be used to reinforce geotechnical materials. The primary benefit of geocells is that lower quality backfill materials can be used instead of crushed stone to provide a temporary repair. This report summarizes a series of laboratory and field experiments performed to evaluate different geocell materials and geometries in combinations with a variety of soils to verify their effectiveness at supporting heavy aircraft loads. Results provide specific recommendations for using geocell technology for backfill reinforcement for emergency airfield repairs.
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Shah, Ayesha, Jan Olek, and Rebecca S. McDaniel. Real Life Experience with Major Pavement Types. Purdue University, 2022. http://dx.doi.org/10.5703/1288284317371.
Повний текст джерелаАнотація:
Pavement performance is a complex issue which depends on many contributing factors. Examining the performance of real-life pavements across the state determines what the actual service lives are for the pavements. For the purposes of this study, only selected LTPP projects were examined, along with a database containing all the historic repair projects completed in Indiana. Pertinent information present in the Indiana Historic Contracts Database was extracted concerning the types of pavement repair and treatments options commonly employed within the state, the time between repairs, etc. These data were used to determine descriptive statistical parameters and was summarized in graph form. Similarly, data about selected LTPP GPS and SPS sites were downloaded from the online website, LTPP InfoPave and a comparative study between companion sites was performed. These data included study site and pavement-related information, such as construction dates, pavement structure details, maintenance and repair history, and pavement distress surveys. These data were used to draw conclusions about the impact of treatment applications, climatic and geologic factors, traffic volume, and pavement structures on pavement performance. Gaps in knowledge about pavement failure modes, distress data, and effectiveness of treatment applications mentioned in the contracts database file hampered efforts to form a complete picture of the effectiveness of treatment options and their timely (or untimely) application. Similarly, details about pavement mixture design and differentiating factors between companion sites prevented researchers from narrowing down the causes leading to the observed pavement distress.
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Collington, Rosie, and William Lazonick. Pricing for Medicine Innovation: A Regulatory Approach to Support Drug Development and Patient Access. Institute for New Economic Thinking Working Paper Series, January 2022. http://dx.doi.org/10.36687/inetwp176.
Повний текст джерелаАнотація:
The United States represents the world’s largest market for pharmaceutical drugs. It is also the only advanced economy in the world that does not regulate drug prices. There is no upper threshold for the prices of medicines in the United States. List prices are instead set by manufacturers in negotiation with supply-chain intermediaries, though some federal programs have degrees of discretion in price determinations. In practice, this deregulated system means that drug prices in the United States are generally far higher than in other advanced economies, adversely affecting patient accessibility and system affordability. In this paper, we draw on the “theory of innovative enterprise” to develop a framework that provides both a critique of the existing pricing system in the United States and a foundation for developing a new model of pricing regulation to support safety and effectiveness through drug development as well as accessibility and affordability in the distribution of approved medicines to patients. We introduce a regulatory approach we term “Pricing for Medicine Innovation” (PMI), which departs dramatically from the market-equilibrium assumptions of conventional (neoclassical) economics. The PMI approach recognizes the centrality of collective investments by government agencies and business firms in the productive capabilities that underpin the drug development process. PMI specifies the conditions under which, at the firm level, drug pricing can support both sustained investment in these capabilities and improved patient access. PMI can advance both of these objectives simultaneously by regulating not just the level of corporate profit but also its allocation to reinvestment in the drug development process. PMI suggests that although price caps are likely to improve drug affordability, there remain two potential issues with this pricing approach. Firstly, in an innovation system where a company’s sales revenue is the source of its finance for further drug development, price caps may deprive a firm of the means to invest in innovation. Secondly, even with adequate profits available for investment in innovation, a firm that is run to maximize shareholder value will tend to use those profits to fund distributions to shareholders rather than for investment in drug innovation. We argue that, if implemented properly, PMI could both improve the affordability of medicines and enhance the innovative performance of pharmaceutical companies.
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Arewa, Moyosore, and Fabrizio Santoro. An Introduction to Digital Tax Payment Systems in Low-and Middle-Income Countries. Institute of Development Studies, December 2022. http://dx.doi.org/10.19088/ictd.2022.019.
Повний текст джерелаАнотація:
National tax administrations are increasingly investing in the digital facilities needed to make it possible for taxpayers to go online both to file their routine tax returns (e-filing) and remit the tax payments due (e-payment). These facilities potentially benefit both taxpayers and tax administrations. This paper first maps the landscape, explaining which filing and payment technologies are used for tax collection in Africa. We then examine why these technologies are not used to their full potential. Some constraints are on the demand side. These include taxpayers’ preferences for cash and in-person relations and low familiarity with and trust in digital technology. Other constraints lie in infrastructure deficits and broader political, regulatory, and institutional factors. Unlocking the full potential of e-filing and e-payment systems thus seems to depend on meeting several pre-conditions, including solid political will, sound regulatory frameworks, reliable payment infrastructure and adequate investment in human capital. However, there is relatively little reliable evidence of the actual effectiveness of e-services in tax collection. We conclude by outlining some research priorities.
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Kelly, Luke. Lessons learnt from humanitarian negotiations with the Taliban, 1996-2001. Institute of Development Studies (IDS), September 2021. http://dx.doi.org/10.19088/k4d.2021.11.
Повний текст джерелаАнотація:
This rapid literature review finds that humanitarian actors responded in a variety of ways to Taliban actions limiting principled aid in the country during the period of their rule (1996-2001). The report is focused on the findings around humanitarian negotiation and the strategy of humanitarian actors in response to Taliban policies limiting women's ability to work for humanitarian organisations or access services. The findings are not intended to imply parallels with the current situation in Afghanistan. Evidence is in the form of a number of evaluations, academic articles and lessons learned papers on negotiating with the Taliban. It discusses the methods of negotiating with the Taliban (e.g. co-ordination, working with the leadership or rank-and-file), the content of negotiations and particularly the question of reaching agreement on women’s rights, as well as humanitarian actors’ negotiating capacity. There is less discussion on the negotiation of specific programmes (e.g. anti-gender-based violence programmes). Due to the different goals and principles of humanitarian actors, as well as different ideas of feasibility, conclusions on the effectiveness of negotiating tactics vary. Strategies therefore cannot be judged as 'successful' without reference to a conception of what is most important in humanitarian programming, and the constraints of the situation. The review highlights lessons on good negotiating practices. The main issue being negotiated was the clash between the Taliban's restrictions on women and humanitarian actors' aim of providing aid to all, including women, according to need. Various strategies were used to persuade the Taliban to consent to principled aid. This review considers aid agency negotiating strategy and tactics, as well as the underlying interests and constraints that may make negotiations more or less successful.
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Kelly, Luke. Lessons Learnt from Humanitarian Negotiations with the Taliban, 1996-2001. Institute of Development Studies (IDS), September 2021. http://dx.doi.org/10.19088/k4d.2021.126.
Повний текст джерелаАнотація:
This rapid literature review finds that humanitarian actors responded in a variety of ways to Taliban actions limiting principled aid in the country during the period of their rule (1996-2001). The report is focused on the findings around humanitarian negotiation and the strategy of humanitarian actors in response to Taliban policies limiting women's ability to work for humanitarian organisations or access services. The findings are not intended to imply parallels with the current situation in Afghanistan. Evidence is in the form of a number of evaluations, academic articles and lessons learned papers on negotiating with the Taliban. It discusses the methods of negotiating with the Taliban (e.g. co-ordination, working with the leadership or rank-and-file), the content of negotiations and particularly the question of reaching agreement on women’s rights, as well as humanitarian actors’ negotiating capacity. There is less discussion on the negotiation of specific programmes (e.g. anti-gender-based violence programmes). Due to the different goals and principles of humanitarian actors, as well as different ideas of feasibility, conclusions on the effectiveness of negotiating tactics vary. Strategies therefore cannot be judged as 'successful' without reference to a conception of what is most important in humanitarian programming, and the constraints of the situation. The review highlights lessons on good negotiating practices. The main issue being negotiated was the clash between the Taliban's restrictions on women and humanitarian actors' aim of providing aid to all, including women, according to need. Various strategies were used to persuade the Taliban to consent to principled aid. This review considers aid agency negotiating strategy and tactics, as well as the underlying interests and constraints that may make negotiations more or less successful.
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Kelly, Luke. Lessons Learnt from Humanitarian Negotiations with the Taliban, 1996-2001. Institute of Development Studies, September 2021. http://dx.doi.org/10.19088/k4d.2021.119.
Повний текст джерелаАнотація:
This rapid literature review finds that humanitarian actors responded in a variety of ways to Taliban actions limiting principled aid in the country during the period of their rule (1996-2001). The report is focused on the findings around humanitarian negotiation and the strategy of humanitarian actors in response to Taliban policies limiting women's ability to work for humanitarian organisations or access services. The findings are not intended to imply parallels with the current situation in Afghanistan. Evidence is in the form of a number of evaluations, academic articles and lessons learned papers on negotiating with the Taliban. It discusses the methods of negotiating with the Taliban (e.g. co-ordination, working with the leadership or rank-and-file), the content of negotiations and particularly the question of reaching agreement on women’s rights, as well as humanitarian actors’ negotiating capacity. There is less discussion on the negotiation of specific programmes (e.g. anti-gender-based violence programmes). Due to the different goals and principles of humanitarian actors, as well as different ideas of feasibility, conclusions on the effectiveness of negotiating tactics vary. Strategies therefore cannot be judged as 'successful' without reference to a conception of what is most important in humanitarian programming, and the constraints of the situation. The review highlights lessons on good negotiating practices. The main issue being negotiated was the clash between the Taliban's restrictions on women and humanitarian actors' aim of providing aid to all, including women, according to need. Various strategies were used to persuade the Taliban to consent to principled aid. This review considers aid agency negotiating strategy and tactics, as well as the underlying interests and constraints that may make negotiations more or less successful.